The present application relates generally to the field of Mobile Satellite Systems (MSS), and, in particular, to enhanced paging techniques in mobile satellite communication systems (MSS).
The majority of terrestrial cellular communications systems have evolved to LTE/4G-LTE systems and beyond with a focus on Internet Protocol (IP) Multimedia services based on Session Initiation Protocol (SIP). SIP is an application level signaling protocol widely used for creating, managing, and terminating real-time multimedia sessions, such as voice calls, video conferencing, and instant messaging in an IP based network. SIP is used for signaling between a user terminal (UT) and the IP Multimedia Subsystem (IMS) as well as between the entities within the IMS. The IMS is a key element in the LTE/4G-LTE architecture that makes it possible to provide ubiquitous cellular access to a wide range of services provided by the Internet, including multimedia, email, and video conferencing. In line with terrestrial evolution, there is interest in evolving MSS to LTE/4G-LTE systems and beyond.
In contrast to a terrestrial cellular communications system, typical MSS operations require line of sight (LOS) with a satellite. Typically, when a UT of an MSS user is inside a building and there is an incoming multimedia session, the UT is unable to receive (and as a consequence, not respond to) an ordinary paging signal. To attempt to overcome this, an enhanced paging technique called “alerting” (which may be referred to as “high penetration alerting” or “HPA” utilizing a “high penetration alerting signal” to convey a “high penetration alert message,” or “high penetration paging” utilizing a “high penetration paging signal” to convey a “high penetration paging message”) may be invoked to notify a UT and a user of the UT of an incoming communication. Examples of alerting are described in U.S. Patent Application Publication Numbers 2014/0045492 (published on Feb. 13, 2014 and entitled “SYSTEM AND METHOD FOR ENHANCED PAGING AND QUALITY OF SERVICE ESTABLISHMENT IN MOBILE SATELLITE SYSTEMS”) and 2014/0093008 (published on Apr. 3, 2014 and entitled “SYSTEM AND METHOD FOR IMPROVED WAVEFORM AND ENHANCED RECEIVER ALGORITHM FOR HIGH PENETRATION ALERTING IN A MOBILE SATELLITE COMMUNICATIONS SYSTEM”), which are incorporated by reference herein in their entireties. Alerting is expensive in terms of satellite communication resources (for example, power and/or bandwidth) needed to reach the users, therefore, there is a desire by MSS operators to use enhanced paging only for specific services such as voice. Information about the type of service is indicated inside a SIP message. However, a satellite base station subsystem (SBSS) entity responsible for paging and alerting user terminals cannot practically read the content of SIP messages, since SIP signaling is compressed and/or encrypted by IMS elements before it reaches SBSS.
There is a need for an enhanced paging (alerting) in MSS-implemented LTE/4G-LTE (which may be referred to as “MSS-LTE”) communications to reach users in disadvantaged areas such as inside a building. Specifically, there is a need for a system and method to enhance paging penetration and use such techniques judiciously to conserves and efficiently utilize limited satellite communication resources.